This systematic review, stimulated by inconsistency in secondary evidence, reports the benefits and harms of breast cancer (BC) screening and their determinants according to systematic reviews. A systematic search, which identified 9,976 abstracts, led to the inclusion of 58 reviews. BC mortality reduction with screening mammography was 15-25% in trials and 28-56% in observational studies in all age groups, and the risk of stage III+ cancers was reduced for women older than 49 years. Overdiagnosis due to mammography was 1-60% in trials and 1-12% in studies with a low risk of bias, and cumulative false-positive rates were lower with biennial than annual screening (3-17% vs 0.01-41%). There is no consistency in the reviews' conclusions about the magnitude of BC mortality reduction among women younger than 50 years or older than 69 years, or determinants of benefits and harms of mammography, including the type of mammography (digital vs screen-film), the number of views, and the screening interval. Similarly, there was no solid evidence on determinants of benefits and harms or BC mortality reduction with screening by ultrasonography or clinical breast examination (sensitivity ranges, 54-84% and 47-69%, respectively), and strong evidence of unfavourable benefit-to-harm ratio with breast self-examination. The reviews' conclusions were not dependent on the quality of the reviews or publication date. Systematic reviews on mammography screening, mainly from high-income countries, systematically disagree on the interpretation of the benefit-to-harm ratio. Future reviews are unlikely to clarify the discrepancies unless new original studies are published. This article is protected by copyright. All rights reserved.
CONTEXT AND OBJECTIVE:: The purpose of screening tests for cancer is to detect it at an early stage in order to increase the chances of treatment. However, their unrestrained use may lead to unnecessary examinations, overdiagnosis and higher costs. It is thus necessary to evaluate their clinical effects in terms of benefits and harm.
DESIGN AND SETTING:: Review of Cochrane systematic reviews, carried out in the Discipline of Evidence-Based Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo.
METHODS:: Cochrane reviews on the clinical effectiveness of cancer screening procedures were included. Study titles and abstracts were independently assessed by two authors. Conflicts were resolved by another two authors. Findings were summarized and discussed.
RESULTS:: Seventeen reviews were selected: fifteen on screening for specific cancers (bladder, breast, colorectal, hepatic, lung, nasopharyngeal, esophageal, oral, prostate, testicular and uterine) and two others on cancer in general. The quality of evidence of the findings varied among the reviews. Only two reviews resulted in high-quality evidence: screening using low-dose computed tomography scans for high-risk individuals seems to reduce lung cancer mortality; and screening using flexible sigmoidoscopy and fecal occult blood tests seems to reduce colorectal cancer mortality.
CONCLUSION:: The evidence found through Cochrane reviews did not support most of the commonly used screening tests for cancer. It is recommended that patients should be informed of the possibilities of false positives and false negatives before they undergo the tests. Further studies to fully assess the effectiveness of cancer screening tests and adverse outcomes are required.
BACKGROUND: Debates about the benefits and harms of mammography continue despite the accumulation of evidence. We sought to quantify the disagreement across systematic reviews of mammography and determine whether author or design characteristics were associated with conclusions that were favourable to the use of mammography for routine breast cancer screening.
METHODS: We identified systematic reviews of mammography published between January 2000 and November 2015, and extracted information about the selection of evidence, age groups, the use of meta-analysis, and authors' professions and financial competing interest disclosures. Conclusions about specific age groups were graded as favourable if they stated that there were meaningful benefits, that benefits of mammography outweighed harms, or that harms were inconsequential. The main outcome measures were the proportions of favourable conclusions relative to review design and author characteristics.
RESULTS: From 59 conclusions identified in 50 reviews, 42% (25/59) were graded as favourable by two investigators. Among the conclusions produced by clinicians, 63% (12/19) were graded as favourable compared to 32% (13/40) from other authors. In the 50-69 age group where the largest proportion of systematic reviews were focused, conclusions drawn by authors without financial competing interests (odds ratio 0.06; 95% CI 0.07-0.56) and non-clinicians (odds ratio 0.11; 95% CI 0.01-0.84) were less likely to be graded as favourable. There was no trend in the proportion of favourable conclusions over the period, and we found no significant association between review design characteristics and favourable conclusions.
CONCLUSIONS: Differences in the conclusions of systematic reviews of the evidence for mammography have persisted for 15 years. We found no strong evidence that design characteristics were associated with greater support for the benefits of mammography in routine breast cancer screening. Instead, the results suggested that the specific expertise and competing interests of the authors influenced the conclusions of systematic reviews.
BACKGROUND: Several popular screening tests, such as mammography and prostate-specific antigen, have met with wide controversy and/or have lost their endorsement recently. We systematically evaluated evidence from randomized controlled trials (RCTs) as to whether screening decreases mortality from diseases where death is a common outcome.
METHODS: We searched three sources: United States Preventive Services Task Force (USPSTF), Cochrane Database of Systematic Reviews, and PubMed. We extracted recommendation status, category of evidence and RCT availability on mortality for screening tests for diseases on asymptomatic adults (excluding pregnant women and children) from USPSTF. We identified meta-analyses and individual RCTs on screening and mortality from Cochrane and PubMed.
RESULTS: We selected 19 diseases (39 tests) out of 50 diseases/disorders for which USPSTF provides screening evaluation. Screening is recommended for 6 diseases (12 tests) out of the 19. We assessed 9 non-overlapping meta-analyses and 48 individual trials for these 19 diseases. Among the results of the meta-analyses, reductions where the 95% confidence intervals (CIs) excluded the null occurred for four disease-specific mortality estimates (ultrasound for abdominal aortic aneurysm in men; mammography for breast cancer; fecal occult blood test and flexible sigmoidoscopy for colorectal cancer) and for none of the all-cause mortality estimates. Among individual RCTs, reductions in disease-specific and all-cause mortality where the 95% CIs excluded the null occurred in 30% and 11% of the estimates, respectively.
CONCLUSIONS: Among currently available screening tests for diseases where death is a common outcome, reductions in disease-specific mortality are uncommon and reductions in all-cause mortality are very rare or non-existent.
La portée de cette étude était d'évaluer la solidité des preuves pour l'indicateur de performance portugaise actuelle sur le cancer du sein par mammographie de dépistage afin de déterminer le groupe d'âge recommandé et la périodicité pour le dépistage. Une recherche d'articles a été menée dans les principales bases de données internationales de la littérature médicale. Les articles publiés entre Janvier 2006 et Janvier 2012 répondant aux objectifs de cet examen ont été inclus. La taxonomie SORT a été utilisé pour classer les résultats. Sur les 253 articles, cinq articles répondaient aux critères d'inclusion et ont été sélectionnés pour examen. Ces comprenaient trois examens systématiques, une méta-analyse et une directive clinique sur la base d'un examen systématique. Une réduction de la mortalité par cancer du sein avec le dépistage de la mammographie a été le résultat dans tous les articles sélectionnés. Le dépistage par mammographie entre 50 et 69 ans a été recommandé dans tous les articles qui évaluent ce groupe d'âge. Les directives cliniques ont recommandé un dépistage tous les deux ans. En conclusion, la littérature actuelle recommande la mammographie pour les femmes tous les deux ans entre les âges de 50 et 69 ans. Ceci est cohérent avec l'indicateur de performance courante pour le dépistage du cancer du sein au Portugal.
IMPORTANCE: Le cancer du sein est la deuxième cause de décès par cancer chez les femmes aux États-Unis. Le dépistage par mammographie peut être associée à la mortalité par cancer du sein réduit, mais peut aussi causer des dommages. Les directives recommandent décisions de dépistage individualisation, en particulier pour les jeunes femmes.
OBJECTIFS: Nous avons examiné les éléments de preuve sur le bénéfice de la mortalité et les dommages principaux de la mammographie de dépistage et ce qui est connu sur la façon de personnaliser les décisions de dépistage par mammographie, y compris la communication des risques et des avantages pour les patients.
Acquisition des données: Nous avons cherché dans MEDLINE, de 1960-2014 à décrire (1) avantages de la mammographie, (2) les inconvénients de la mammographie, et (3) l'individualisation des décisions de dépistage et de promouvoir la prise de décisions éclairées. Nous avons également cherché manuellement la liste des articles clés récupérées, commentaires sélectionnés, les méta-analyses et recommandations de bonnes pratiques de référence. Nous avons évalué le niveau de preuve en utilisant les directives de l'American Heart Association.
RÉSULTATS: Le dépistage par mammographie est associée à une réduction globale de 19% de la mortalité par cancer du sein (environ 15% pour les femmes dans leur 40s et 32% pour les femmes dans leur 60s). Pour un 40 - femme ou 50 ans de subir 10 ans de mammographies annuelles, le risque cumulatif d'un résultat faussement positif est d'environ 61%. Environ 19% des cancers diagnostiqués au cours de cette période de 10 ans ne serait pas devenu cliniquement apparente sans dépistage (surdiagnostic), mais il existe une incertitude sur cette estimation. Le bénéfice net du dépistage dépend grandement sur le risque de cancer du sein référence, qui devraient être incorporées dans les décisions de dépistage. aides à la décision ont le potentiel d'aider les patients à intégrer l'information sur les risques et les avantages avec leurs propres valeurs et priorités, même si elles ne sont pas encore largement disponibles pour une utilisation dans la pratique clinique.
CONCLUSIONS ET PERTINENCE: Pour maximiser les avantages de la mammographie de dépistage, les décisions doivent être individualisées en fonction des profils et des préférences de risque des patients. Les modèles de risque et aide à la décision sont des outils utiles, mais d'autres recherches sont nécessaires pour optimiser ces ainsi que de quantifier surdiagnostic. La recherche devrait également explorer d'autres stratégies de dépistage du cancer du sein.
This systematic review, stimulated by inconsistency in secondary evidence, reports the benefits and harms of breast cancer (BC) screening and their determinants according to systematic reviews. A systematic search, which identified 9,976 abstracts, led to the inclusion of 58 reviews. BC mortality reduction with screening mammography was 15-25% in trials and 28-56% in observational studies in all age groups, and the risk of stage III+ cancers was reduced for women older than 49 years. Overdiagnosis due to mammography was 1-60% in trials and 1-12% in studies with a low risk of bias, and cumulative false-positive rates were lower with biennial than annual screening (3-17% vs 0.01-41%). There is no consistency in the reviews' conclusions about the magnitude of BC mortality reduction among women younger than 50 years or older than 69 years, or determinants of benefits and harms of mammography, including the type of mammography (digital vs screen-film), the number of views, and the screening interval. Similarly, there was no solid evidence on determinants of benefits and harms or BC mortality reduction with screening by ultrasonography or clinical breast examination (sensitivity ranges, 54-84% and 47-69%, respectively), and strong evidence of unfavourable benefit-to-harm ratio with breast self-examination. The reviews' conclusions were not dependent on the quality of the reviews or publication date. Systematic reviews on mammography screening, mainly from high-income countries, systematically disagree on the interpretation of the benefit-to-harm ratio. Future reviews are unlikely to clarify the discrepancies unless new original studies are published. This article is protected by copyright. All rights reserved.
